1. Field of the Invention
This invention relates to a portable oxygen generator and, in particular, a portable oxygen generator which produces gaseous oxygen by a process of decomposition of aqueous hydrogen peroxide using a catalyst of embossed metallic lead strips.
2. Description of the Prior Art
Oxygen gas is used in scientific, medical and industrial procedures and there is a need for a relatively light and portable generating system. The development of a portable system has been disclosed in U.S. Pat. No. 4,792,435, entitled OXYGEN GENERATING SYSTEM which issued Dec. 20, 1988 to Nakajima Dokosho Company Limited of Tokyo, Japan in respect of an invention made by Nakajima, Masahiko, of Tokyo, Japan. As described in the abstract of this patent, the invention disclosed is an oxygen generating system for continuously generating oxygen gas by the catalytic decomposition of an aqueous hydrogen peroxide that includes a catalyst having a platinum group catalyst component carried on a highly porous sintered ceramic support of a large pore size and a reaction chamber for accommodating the catalyst. The system further includes a control device for controlling the operation of the hydrogen peroxide supplying based on a detection signal from a pressure sensor for detecting the pressure of the generated oxygen gas. The oxygen generating system is compact and reduced in weight due to the catalytic decomposition of hydrogen peroxide at high concentration, which can be carried out effectively and safely under an increased temperature.
Other relevant prior art includes U.S. patents:
______________________________________ 3,887,696 6/1975 Bernard et al. 3,917,461 11/1975 Kuhl et al. 4,315,732 2/1982 Rowbottam et al. 4,466,556 8/1984 Sochting 4,488,951 12/1984 Nolan et al. 4,601,884 7/1986 Coeckelsberghs et al. ______________________________________
and Japanese patents:
______________________________________ 42155 10/1977 26445 7/1978 49843 11/1981 ______________________________________
and United Kingdom patent 2056310 dated Mar. 19, 1981.
Aqueous hydrogen peroxide produces a large mount of oxygen per unit volume and is known as a means to reduce the size and the weight of an oxygen generator as compared, for example, to a high pressure oxygen gas cylinder. Japanese Utility Model Publication No. 26445/1980 discloses an oxygen gas generating system adapted to catalytically decompose aqueous hydrogen peroxide by using a manganese compound as a catalyst. This has been pointed out by Nakajima that the decomposing reaction proceeds explosively if the concentration of hydrogen peroxide exceeds about 5 w/w %. However, higher concentrations are necessary to achieve practical utility in a portable supply of aqueous hydrogen peroxide.
A platinum type catalyst for decomposing aqueous hydrogen peroxide at a higher concentrations was disclosed in Japanese Patent Publication No. 42155/1977. However, Nakajima teaches that this catalyst is not satisfactory given the required reaction area and defoliation problems and that prior to his patent that no effective practical means were available. Thus, he teaches that the catalyst layer on the support tends to be deteriorated with the increase of the gas pressure inside the support and to be washed out by the aqueous hydrogen peroxide.
It is also known to have a system of controlling the flow rate of hydrogen peroxide by adjusting a valve for supplying aqueous hydrogen peroxide depending on the pressure of the generated oxygen gas by means of a mechanical link. (See Japanese Patent Publication No. 49843/1981). Nakajima discloses a pressure sensor for detecting the pressure of the Oxygen gas and a water level sensor for detecting the water level in the gas/water separator attached to the separator. The sensors disclosed are semiconductor sensors or mechanical diaphragm sensors. A control unit controls a pump depending on the signal from the pressure sensor.